It is known in the art that a band plate, which is un-rolled from a coil, is bent so as to form a corrugated plate. According to such known art, multiple punches arranged in a plate feeding direction of the band plate are sequentially pushed down to the band plate to form the corrugated plate. The corrugated plate has multiple projections arranged in the plate feeding direction, wherein each of the projections extends in a width direction of the band plate. The corrugated plate thus manufactured is used as a heat absorbing element or a heat radiating element of a heat exchanger. It is necessary to change a length of the corrugated plate, that is, a length of the projection in a longitudinal direction of the projection, depending on each type of the heat exchanger, to which the corrugated plate is applied.
According to the above conventional method for manufacturing the corrugated plate, the length of the projection in its longitudinal direction is decided by a width of the band plate. Therefore, it is necessary to stop a production line to exchange the coil for the band plate, in order to change the width of the band plate, that is, the length of the projection in its longitudinal direction. It is a problem that production efficiency is decreased.
According to another prior art, for example, as disclosed in Japanese Patent Publication No. H10-197180, a press portion has multiple bending punches arranged in a width direction of a band plate and multiple press portions are provided in a plate feeding direction of the band plate. A flat-plate portion of the band plate is bent step by step in the plate feeding direction by multi-stage bending processes, so that a corrugated plate is formed, wherein the corrugated plate has multiple projections arranged in the width direction and each of the projections extends in the plate feeding direction. According to the above manufacturing method, when a cutting portion of the band plate in the plate feeding direction is changed, it is possible to manufacture different kinds of the corrugated plates having different lengths of the projections in the longitudinal direction of the projection without changing the coil for the band plate.
It is, however, a problem that a length of a manufacturing line becomes longer because the multiple press portions are provided in the plate feeding direction.